Translating Sentences into Equations and Solving - Alamo Colleges District

Math0301

Translating Sentences into Equations and Solving

Objective A: To translate a sentence into an equation and solve

An equation states that two mathematical expressions are equal. Therefore, to translate a sentence into an equation requires recognition of the words or phrases that mean "equals." Some of these phrases are

equals

is is equal

translate

to

" ="

amounts

represents

Once the sentence is translated into an equation, the equation can be simplified to one of the form variable = constant and the solution is found.

Example 1: Translate "three more than twice a number is seventeen" into an equation and solve.

Step 1: Assign a variable to the unknown quantity. Let the unknown number = n

Step 2: Find two verbal expressions for the same value.

Three more than twice a number is seventeen

Step 3: Write a mathematical expression for each verbal expression. Write the equals sign.

Three more than twice a number is

seventeen

3

+

2n

=

17

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Step 4: Solve the resulting equation.

3 + 2n - 3 = 17 - 3 2n = 14 2n = 14 22 n = 7

The number is seven.

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* subtract 3 from both sides of the equation * divide both sides of the equation by 2

Example 2: Translate "a number decreased by eight equals twelve" into an equation and solve.

Step 1: Assign a variable to the unknown quantity. Let the unknown number = x

Step 2: Find two verbal expressions for the same value.

A number decreased by eight equals twelve

Step 3: Write a mathematical expression for each verbal expression. Write the equals sign. A number decreased by eight equals twelve

x

-

8

=

12

Step 4: Solve the equation

x - 8 = 12 x - 8 + 8 = 12 + 8

x = 20

The number is twenty.

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Example 3: The quotient of a number and six is five. Find the number. Step 1: Assign a variable to the unknown quantity.

Let the unknown number = z Step 2: Find two verbal expressions for the same value.

The quotient of a number and six is five

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Step 3: Write a mathematical expression for each verbal expression. Write the equals sign.

The quotient of a number and six is five

z

=

5

6

*use fractions when converting the word "quotient" into a mathematical equation

Step 4: Solve the equation.

z =5 6

6? z = 6?5 6

Multiply each side of the equation by our denominator of 6

z = 30

The number is 30.

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Math0301

Example 4: Eight decreased by twice a number is four. Step 1: Assign a variable to the unknown quantity.

Let the unknown number = t Step 2: Find two verbal expressions for the same value.

Eight decreased by twice a number

is

four

Step 3: Write a mathematical expression for each verbal expression. Write the equals sign.

Eight decreased by twice a number

is

four

8

-

2t

Step 4: Solve the equation. 8 - 2t

The number is 2.

=

4

=

4

8 - 8 - 2t = 4 - 8

- 2t = -4

- 2t = - 4 -2 -2

t=2

Example 5: Three less than the ratio of a number to seven is one. Find the number.

Step 1: Assign a variable to the unknown quantity. Let the unknown number = x

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Step 2: Find two verbal expressions for the same value. Three less than the ratio of a number to seven is one

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Step 3: Write a mathematical expression for each verbal expression. Write the equals sign. Three less than the ratio of a number to seven is one

x - 3

7

= 1

Step 4: Solve the equation.

x -3

=

1

7

x -3+3 =1+3 7

x =4 7

7 x =74 7

x = 28

The number is 28.

Example 6:

The cost of a television with remote control is $649. This amount is $125 more than the cost without remote control. Find the cost of the television without remote control.

Strategy

To find the cost of the television without remote control, write and solve an equation using C to represent the cost of the television without remote control.

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